Recently, it has been realized that the use of a signaling network is important for next generation intelligent optical networks for providing services like real time point-and-click provisioning of optical channels, optical layer protection and restoration, optical layer network topology auto-discovery and optical layer bandwidth management. However, the performance and reliability of any signaling network (referred to herein as a control plane) is very important for successful deployment and usage of these services.
For a number of reasons, such as easier feature enhancement and wider access of features to customers, the Internet Protocol (IP) has been emerging as the technology of choice to implement a control plane for Optical Transport Networks (OTNs). Unfortunately, the use of an IP-based control plane is not without its problems. For example, one form of routing used in an IP-based control plane is open shortest path first (OSPF) routing. Detection of a failure in OSPF relies on “hello” messages and the expiration interval of timers associated with these hello messages. Given this, time to detect a failure is dictated by two factors. First, the frequency of hello messages, which must be computed while keeping in mind that resources, such as bandwidth and processing, required for them should not affect real traffic. Second, expiration values of timers, which must be chosen while realizing that congestion situations in the network should not be interpreted as failures. In practice, OSPF is slow to converge since the time between hello messages and the expiration timer values, for a reasonable size network, are typically chosen on the order of seconds which makes the OSPF convergence time (failure detection+update of routing tables) on the order of several seconds (or sometimes maybe a few minutes). In case of a failure in such an IP-based control plane, this slow convergence of OSPF routing degrades the setup time performance of new or existing connection requests in the system from on the order of tens of milliseconds to several seconds or minutes. Moreover, when the IP-based control plane failure is coupled with an OTN failure then restoration performance of the system gets severely impacted—a situation that customers may perceive as intolerable.